In 1986 I built a Wilmslow Audio speaker kit based on the Kef 203 design. Do the non-polarised caps in these have a limited lifetime like the capacitors used in regular circuits? What are the symptoms (if any) of an aging cap?
Also does anyone know the composition of the plasticy film that covers the main driver cone? It looks like it was sprayed or painted on. Many years ago I made a less than successful attempt to repair a small area that has been damaged. Can the film be removed entirely and recoated? (The cone itself is undamaged.)
Here's a pic of the KEF original, mine doesn't have the fancy wood veneer as the kit came as unfinished MDF which I painted white.
Here's the marketing brochure http://www.kef.com/uploads/files/en/museum_pdf/80s/Model_203.pdf
Also does anyone know the composition of the plasticy film that covers the main driver cone? It looks like it was sprayed or painted on. Many years ago I made a less than successful attempt to repair a small area that has been damaged. Can the film be removed entirely and recoated? (The cone itself is undamaged.)
Here's a pic of the KEF original, mine doesn't have the fancy wood veneer as the kit came as unfinished MDF which I painted white.
Here's the marketing brochure http://www.kef.com/uploads/files/en/museum_pdf/80s/Model_203.pdf
If the caps are electrolytics then it wont do any harm to replace them with some new ones. Although replacing electolytic caps with polypropylene can improve the sound, the lower ESR of polyprop can change the frequency response and actually sound worse.
The other thing that can degrade over time is the ferrofluid in the tweeters can stiffen up (assuming they have ferrofluid in them).
I'd leave the cone alone.
The other thing that can degrade over time is the ferrofluid in the tweeters can stiffen up (assuming they have ferrofluid in them).
I'd leave the cone alone.
If the current crossover caps are non polar film types then leave well enough alone. If they are non polar electrolytics then you can replace with the same or with film types. The sound will change whichever you choose as the sound you are currently hearing may have dulled over time.
Failing electrolytic caps can make the speaker sound dull due to increasing equivalent series resistance (ESR).
The main driver cone is made of Bextrene which was a polymer intended as consumer packaging material. It was thermoformed into the cone shape and, as far as I am aware, does not have a surface coating of any kind.
Failing electrolytic caps can make the speaker sound dull due to increasing equivalent series resistance (ESR).
The main driver cone is made of Bextrene which was a polymer intended as consumer packaging material. It was thermoformed into the cone shape and, as far as I am aware, does not have a surface coating of any kind.
Having said that, I've just read that damping layers were added to bextrene cones to suppress serious mid-band break up. Bextrene cones were seemingly coated in 'plastiflex' to dampen resonances, particularly on the back of the cone - the front coating was more for cosmetic reasons, it could be pealed off and recoated. See the reference below:
SpeakerTalk :: View topic - Bextrene Cone Coatings
SpeakerTalk :: View topic - Bextrene Cone Coatings
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Yes, replace them. 🙂
But, modern caps have lower ESR's than what was commonly used in the 1980's.
Measure the ESR and add resistance if needed, especially in shunt (going to ground).
I've heard good thing about the Mundorf electrolytics.
But, modern caps have lower ESR's than what was commonly used in the 1980's.
Measure the ESR and add resistance if needed, especially in shunt (going to ground).
I've heard good thing about the Mundorf electrolytics.
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